(a) Field of the Invention
The present invention relates to a method for detecting road slope and a system for controlling vehicle speed using the method. More particularly, the present invention relates to a method for detecting a road slope using road image information provided by a camera, and to a system that performs vehicle speed control on the basis of whether a road slope has been detected.
(b) Description of the Related Art
An ever-increasing amount of electronic control is being used in vehicles to provide greater safety and convenience. Such electronic control is fully automatic and often entails various determinations of driving conditions, on the basis of which operation is performed. The ABS (anti-lock brake system), TCS (traction control system), and cruise control system are some common examples.
An important such determination of a driving condition is that of identifying an approaching upward or downward slope in the road. If an approaching slope in the road is not identified with the use of the cruise control system, for example, vehicle speed may fall well below the set speed in the case of an uphill slope and well above the set speed in the case of a downhill slope. That is, using the uphill example, without detection of the approaching slope in the road, no adjustments prior to the uphill slope are made such that the vehicle loses speed. Although the drop in speed is detected then compensated for, a substantial amount of time is often required to recover the set speed.
Conventional methods to detect a slope in the road include the use of instruments such as a level meter, G-sensor, etc. that are mounted to the vehicle to detect changes in the horizontal positioning of the vehicle, and include processes in which vehicle operation is detected and modeling of the vehicle operation is performed to determine if the vehicle is traveling on a slope in the road. However, in the case of the level meter, the instrument is expensive and responds slowly. The G-sensor, on the other hand, is error prone as a result of noise elements caused by shock received from the road. In vehicle modeling, the process of calculating variables used is complicated such that errors are often found in the calculated results.
The present invention has been made in an effort to solve the above problems.
It is an object of the present invention to provide a method for detecting a road slope using road image information provided by a camera, and to a system that uses the detected road slope for controlling vehicle speed.
To achieve the above object, the present invention provides a method for detecting road slope and a system for controlling vehicle speed using the method. The method comprising the steps of (a) receiving input of road images from a camera; (b) performing conversion of the road images into a bird""s-eye view; (c) extracting a plurality of lane markers from the converted road images; (d) calculating a slope in the extracted lane markers; and (e) calculating a slope in the road using a difference in value between the slopes.
According to a feature of the present invention, the slope in the road is calculated by selecting two lane marker slopes of lane markers on opposite sides of the road, and calculating a difference in value between the slopes.
According to another feature of the present invention, in step (b) of conversion into a bird""s-eye view, only data in a relevant area including left and right lane markers that define a lane are converted.
According to yet another feature of the present invention, the method further comprises the step of determining if a steering angle is within a predetermined range by receiving input from a steering angle sensor, wherein the steering angle determination may be performed before any of the steps (a)-(e), and wherein if it is determined that the steering angle falls outside the predetermined range, remaining steps of the method are not performed.
The system for controlling vehicle speed comprises a vehicle speed setting unit for establishing a target vehicle speed and outputting the same; a camera for obtaining road images and outputting the same; a drive state detecting unit having a plurality of sensors for detecting a vehicle drive state; an actuator unit for performing specific automatic controls of the vehicle; and a control unit for performing the above-described method of the present invention to detect a road slope, and controlling the actuator unit according to road slope detection results such that the vehicle is maintained at the established speed.
According to a feature of the present invention, the actuator unit includes a throttle valve actuator for controlling a throttle valve according to control signals received from the control unit, and wherein the throttle valve actuator is a step motor.
According to another feature of the present invention, the control unit, if it is determined that there is an approaching upward slope in the road, outputs a control signal to the throttle valve actuator such that an opening of the throttle valve is increased, and if it is determined that there is an approaching downward slope in the road, the control unit outputs a control signal to the throttle valve actuator such that the opening of the throttle valve is decreased.